yeah thats why i mentioned it. not sure though. here is a link about Fe but even this says Fe without macros can increase micros. the coverting from Fe1 to Fe2 or Fe3 and the use of each in aglae is not really understood. then we dont know if its inorganic or organic Fe. a lot of unknowns here. free Fe is more known, Fe compounds has not been tested as much.
ooppsss forgot the link,lol;
Chemistry and the Aquarium